KR102210618B1 - Hexagonal boron nitride powder and its manufacturing method, and composition and heat dissipating material using the same - Google Patents

Abstract

Hexagonal boron nitride (h-BN) powder capable of imparting high thermal conductivity and high dielectric strength to the insulating heat dissipating material when used as a filler for an insulating heat dissipating material such as resin, and its manufacturing method, the h-BN powder It provides a composition using, and a heat dissipating material excellent in thermal conductivity and insulation resistance. As an impurity element, the boron content is 1.00 to 30.00 mass%, the oxygen content is 0 to 1.00 mass%, the particle size distribution curve has a peak (A) within a predetermined particle size range, and a 50% volume cumulative particle diameter D ₅₀ (d1 ) Is 30.0 to 200.0 μm, and the ratio of the height (a1) of the peak (A) before treatment and the height (a2) of the peak A after treatment when the h-BN powder is ultrasonicated for 1 minute under predetermined conditions is 0.80 H-BN powder containing agglomerates of primary particles of h-BN whose ratio of D ₅₀ (d1) before treatment and D ₅₀ (d2) after treatment is 0.80 to 1.00 is used.

Description

Hexagonal boron nitride powder and its manufacturing method, and composition and heat dissipating material using the same

The present invention relates to an h-BN powder comprising an aggregate of primary particles of hexagonal boron nitride (hereinafter, also referred to as "h-BN"), a method for producing the same, and a composition and a heat dissipating material using the h-BN powder. About.

The h-BN particles have a graphite-like layered structure, and are excellent in properties such as thermal conductivity, electrical insulation, heat resistance, corrosion resistance, and lubrication/release properties. For this reason, it is used as a filler for insulating heat dissipating materials such as resin and rubber (hereinafter, also referred to as "resin etc."), solid lubricants, solid release agents, raw materials for manufacturing h-BN sintered bodies, and the like.

As a method for producing the h-BN powder, (1) a method of directly nitriding boron using nitrogen or ammonia, (2) a method of reacting boron halide with ammonia or an ammonium salt, and (3) a boron compound such as boron oxide. A method of reducing nitriding by reacting with a nitrogen-containing organic compound such as melamine, (4) a method of reducing nitriding by heating a boron compound with a carbon source at a high temperature of 1600°C or higher in a nitrogen atmosphere.

In addition, from the viewpoint of improving the thermal conductivity and insulation properties of the insulating heat-dissipating material when added to resin as a filler of the insulating heat-dissipating material, various proposals having a specific shape and particle diameter as effective h-BN particles or h-BN powders Has been.

For example, in Patent Document 1, a resin molded body having high thermal conductivity (heat-radiating sheet) by using h-BN powder having a cardhouse structure, which has a large crystallite diameter and a large orientation in a predetermined crystal plane of the primary particles. What can be produced is described.

In addition, in Patent Document 2, according to the h-BN particles having a polyhedral structure, the thermal anisotropy in the plane direction originally possessed by the h-BN crystal is reduced, and high thermal conductivity is expressed when the resin is filled, and the insulating property of the resin is It is described that the degradation is reduced.

International Publication No. 2015/119198 Japanese Patent Publication No. 2017-14064

As described in Patent Document 1, the h-BN powder having a large specific orientation of the primary particles and a large crystallite diameter has a large specific surface area, and a large number of fine pores are easily formed between the aggregated particles, This causes a decrease in the insulating properties of a molded article such as an added resin.

On the other hand, the h-BN particles having a polyhedral structure having a polyhedral structure as described in Patent Document 2 have a small specific surface area, so that voids as described above are unlikely to occur, but sufficient cohesive strength cannot be obtained. For this reason, when producing a molded body by adding a resin or the like, each surface of the polyhedron of the polyhedral structure is oriented by external force, and the thermal conductivity of the molded body is liable to decrease.

The present invention has been made to solve the above problems, and when used as a filler for an insulating heat dissipating material such as resin, h-BN powder capable of imparting high thermal conductivity and high dielectric strength to the insulating heat dissipating material, and the like. It aims to provide a manufacturing method. In addition, it is also an object of the present invention to provide a composition using the h-BN powder, and a heat dissipating material excellent in thermal conductivity and insulation.

In the present invention, in the h-BN powder containing the aggregate of the primary particles of h-BN, it is obtained by going through a step of melting the surface of the granulated powder, and having a predetermined particle size distribution and a cohesive strength, such as a resin. When used as a filler for an insulating heat dissipating material, it is based on finding that the said insulating heat dissipating material expresses high thermal conductivity and high dielectric strength.

That is, the present invention provides the following [1] to [10].

[1] A hexagonal boron nitride powder containing an agglomerate of primary particles of hexagonal boron nitride, wherein the content of boron as an impurity element is 1.00 to 30.00 mass%, the oxygen content is 0 to 1.00 mass%, based on volume In the particle size distribution curve showing the frequency distribution, the particle size has a peak within the range of 10.0 μm or more and less than 100.0 μm, and the 50% volume cumulative particle diameter D ₅₀ (d1) is 30.0 to 200.0 μm, and the hexagonal boron nitride powder is subjected to the following conditions. The ratio (a2/a1) of the peak height (a1) before treatment and the peak height (a2) after treatment when ultrasonicated for 1 minute is 0.80 to 1.00, and 50% volume accumulation before treatment Hexagonal boron nitride powder having a ratio (d2/d1) of a particle diameter D ₅₀ (d1) and a 50% volume cumulative particle diameter D ₅₀ (d2) after treatment is 0.80 to 1.00.

[Condition 1] In a 50 mL glass beaker having a body inner diameter of 40 mm and a height of 60 mm, 0.06 g of the hexagonal boron nitride powder, detergent ("Marmaremon (registered trademark)", manufactured by Lion Corporation) 0.005 g and water (20) ℃) 50g of the mixed powder sample dispersion is put, and the tip of the ultrasonic generator's vibrator is set at a height of 1cm from the bottom of the center of the beaker, and ultrasonically treated with an output of 150W and an oscillation frequency of 19.5 kHz.

[2] The hexagonal boron nitride powder according to [1], wherein the BET specific surface area is 0.1 m 2 /g or more and less than 5.0 m 2 /g, and the surface of the primary particles is a turtle shell shape.

[3] The hexagonal boron nitride powder according to [1] or [2], wherein the crystallite diameter derived from the (002) plane of hexagonal boron nitride determined by powder X-ray diffraction measurement is 250 Å or more and less than 375 Å.

[4] A method for producing the hexagonal boron nitride powder according to any one of the above [1] to [3], comprising: a boron powder and one or two or more boron compounds selected from boron oxoic acid and boron oxide. Step 1 of preparing a mixed powder containing, Step 2 of obtaining a temporary fired powder by temporarily firing the mixed powder at 1200°C or more and less than 1800°C in a rare gas atmosphere, and Granulating the temporary fired powder to have a particle diameter of 10 to Step 3 of obtaining a 200 µm granulated powder, step 4 of obtaining a molten powder by melting the granulated powder at 1800 to 2300°C under a rare gas atmosphere, and a step 4 of obtaining a molten powder at 2000 to 2300°C under a nitrogen gas atmosphere A method for producing a hexagonal boron nitride powder having step 5 of firing to obtain a hexagonal boron nitride powder.

[5] The method for producing the hexagonal boron nitride powder according to [4], wherein the temporary calcination powder obtained in the step 2 contains boron oxyoxide.

[6] The method for producing a hexagonal boron nitride powder according to [4] or [5], wherein in the step 3, at least one of boron oxide and hexagonal boron nitride is added to the temporary calcined powder and granulated.

[7] A composition comprising a substrate comprising one or two or more selected from resins and rubbers, and the hexagonal boron nitride powder according to any one of the above [1] to [3].

[8] A heat dissipating material comprising the composition according to [7].

[9] The heat radiation material according to [8], which is a heat radiation sheet.

[10] The diffraction peak intensity (I(002)) and (100) plane of the (002) plane of the primary particles of hexagonal boron nitride obtained by X-ray diffraction measurement in a direction perpendicular to the thickness direction of the heat dissipation sheet The heat dissipating material according to [9], wherein the ratio (I(002)/I(100)) of the diffraction peak intensity (I(100)) of is 7.0 to 15.

Advantageous Effects of Invention According to the present invention, when used as a filler for an insulating heat dissipating material such as resin, it is possible to provide h-BN powder capable of imparting high thermal conductivity and high dielectric strength to the insulating heat dissipating material and a method for producing the same.

Therefore, it is possible to provide a heat dissipating material excellent in thermal conductivity and insulation by the composition of the present invention using the h-BN powder.

1 is a diagram showing a change in a particle size distribution curve by ultrasonic treatment of h-BN powder of Example 1, and the left is before ultrasonic treatment and the right is after ultrasonic treatment.
2 is a view showing a change in the particle size distribution curve by ultrasonic treatment of h-BN powder of Comparative Example 2, and the left is before ultrasonic treatment and the right is after ultrasonic treatment.
3 is a diagram schematically showing a mode of ultrasonic treatment in condition 1 according to the present invention.
Fig. 4 is a scanning electron microscope (hereinafter abbreviated as "SEM") image (1500 times magnification) of the surface of the primary particles of h-BN in the h-BN powder of the present invention.
5 is a cross-sectional SEM image (magnification of 5000 times) of primary particles of h-BN in the h-BN powder of the present invention.
6 shows the X-ray diffraction spectrum of the temporary baking powder in Production Example 1. FIG.
7 is an SEM image (magnification of 10000 times) of the temporary baking powder in Production Example 1. FIG.
8 is an SEM image (magnification 500) of molten powder in Production Example 1. FIG.
9 shows an X-ray diffraction spectrum of the h-BN powder of Example 1.

Hereinafter, the h-BN powder of the present invention, a method for producing the same, and a composition and a heat dissipating material using the h-BN powder will be described in detail.

[Hexagonal boron nitride (h-BN) powder]

The h-BN powder of the present invention contains agglomerates of primary particles of h-BN. The h-BN powder has a boron content of 1.00 to 30.00 mass% as an impurity element and an oxygen content of 0 to 1.00 mass%. And in the particle size distribution curve showing the frequency distribution on a volume basis, the peak is in the range of 10.0 µm or more and less than 100.0 µm, and a 50% volume cumulative particle size D ₅₀ (hereinafter, simply referred to as "D ₅₀ ") (d1 ) Is 30.0 to 200.0 μm. In addition, when the h-BN powder was subjected to ultrasonic treatment for 1 minute under the following condition 1, the ratio (a2/a1) of the peak height (a1) before treatment and the peak height (a2) after treatment was 0.80 to 1.00 In addition, the ratio (d2/d1) of D ₅₀ (d1) before treatment and D ₅₀ (d2) after treatment is 0.80 to 1.00.

[Condition 1] In a 50 mL glass beaker having a body inner diameter of 40 mm and a height of 60 mm, 0.06 g of the hexagonal boron nitride powder, detergent ("Marmaremon (registered trademark)", manufactured by Lion Corporation) 0.005 g and water (20) ℃) 50g of the mixed powder sample dispersion was added, and the tip of the ultrasonic generator's vibrator chip was set at a height of 1cm from the bottom of the center of the beaker, and ultrasonically treated with an output of 150W and an oscillation frequency of 19.5 kHz.

The h-BN powder that satisfies the above requirements has an appropriate particle size and has a large cohesive strength of the agglomerates of the h-BN primary particles, whereby the h-BN powder is used as an insulating heat dissipating material such as a resin. When used as a filler, high thermal conductivity and high dielectric strength can be imparted to the insulating heat dissipating material.

(Content of impurities in h-BN powder)

The h-BN powder of the present invention has a boron content of 1.00 to 30.00 mass% and an oxygen content of 0 to 1.00 mass% as an impurity element.

The oxygen content in the h-BN powder is 1.00 mass% or less, preferably 0.50 mass% or less, more preferably 0.20 mass% or less.

Oxygen atoms may inevitably be included in the h-BN powder, but the oxygen content is preferably as small as possible. When the oxygen content is small, the effect on the curing of the resin or the like can be suppressed when the h-BN powder is added to a resin or the like and used.

The oxygen content can be measured by placing a sample of the h-BN powder in a graphite crucible, melting it in helium gas, and detecting the generated carbon monoxide or carbon dioxide by an infrared absorption method and converting it into an oxygen atom mass. Oxygen atoms in the sample are detected in the form of carbon monoxide or carbon dioxide by bonding with carbon atoms constituting the crucible. Specifically, as shown in the following examples, from the value measured using a nitrogen-oxygen analyzer ("TC-600", manufactured by LECO Japan Co., Ltd.), the oxygen content (q _O ) in the h-BN powder is Is obtained.

Further, the content of boron as an impurity element in the h-BN powder, i.e., boron atom not bound to nitrogen atom and not constituting the h-BN molecule is 1.00 to 30.00 mass%, preferably 5.00 to 28.00 mass% %, more preferably 10.00 to 25.00 mass%.

When the boron content is 1.00% by mass or more, the surface of the h-BN primary particles is smoothed, and high thermal conductivity can be imparted when the h-BN powder is added to a resin or the like. In addition, when it is 30.00 mass% or less, when the said h-BN powder is added to resin etc., sufficient dielectric strength can be provided.

The content of boron as an impurity element in the h-BN powder (q _B) is regarded as a value (qq _O) obtained by subtracting the oxygen content _(O q) from the total impurity content (q). Moreover, the total impurity content (q) is calculated|required as follows.

First, in the same manner as the above-described measurement of the oxygen content (q _O ), when a sample of the h-BN powder is placed in a graphite crucible and melted in helium gas at 2700° C. or higher, nitrogen in the sample is released as nitrogen gas. This nitrogen gas is measured by detecting it with a thermal conductivity detector. Specifically, as shown in the following examples, the value measured using a nitrogen-oxygen analyzer ("TC-600", manufactured by LECO Japan Co., Ltd.) is used as the nitrogen content (q _N ) in the h-BN powder. do.

Purity (p) of the h-BN powder according to the following formula (1) using the values of the measured value of nitrogen content (q _N ), molecular weight of h-BN: 24.818, and atomic weight of nitrogen (N): 14.007 Is obtained, and the total impurity content (q) is calculated by the following formula (2).

p [mass%] = (q _N [mass%]) x 24.818/14.007 (1)

q[% by mass]=100-p (2)

(Particle size distribution)

Fig. 1 shows an example of a particle size distribution curve showing a volume-based frequency distribution of the h-BN powder of the present invention. The upper side of the center arrow of FIG. 1 is a particle size distribution curve before ultrasonic treatment for 1 minute under the following condition 1, and the lower side of the center arrow of FIG. 1 is a particle size distribution curve after the ultrasonic treatment. In addition, the particle size distribution curve of Fig. 1 is shown for the h-BN powder of Example 1 (Production Example 1) described later.

As shown in Fig. 1, the h-BN powder of the present invention has a peak (A) within a range of 10.0 µm or more and less than 100.0 µm in a particle size distribution curve showing a frequency distribution on a volume basis, and D ₅₀ ( d1) is 30.0 to 200.0 μm.

The particle diameter in the range of 10.0 µm or more and less than 100.0 µm and the powder in the vicinity of the peak (A) is considered to be an aggregate of h-BN primary particles. The particle diameter at the position where the peak (A) appears is preferably 20.0 µm or more and less than 95.0 µm, and more preferably 20.0 µm or more and less than 90.0 µm.

Since the position at which the peak (A) appears is in the particle size range, the h-BN powder is suitable for imparting high thermal conductivity and high dielectric strength to the resin and the like, and is also excellent in handling properties when added to the resin or the like.

The h-BN powder has a D ₅₀ (d1) of 30.0 to 200.0 μm, preferably 40.0 to 150.0 μm, and more preferably 50.0 to 100.0 μm.

When d1 is within the above range, the h-BN powder is suitable for imparting high thermal conductivity and high dielectric strength to the resin or the like, and is also excellent in handling properties when added to the resin or the like.

In addition, the ratio of the height (a1) of the peak (A) before treatment and the height (a2) of the peak (A) after treatment (a2/a1) when the h-BN powder was sonicated for 1 minute under the condition 1 Is 0.80 to 1.00, and the ratio (d2/d1) of D ₅₀ (d1) before treatment and D ₅₀ (d2) after treatment is 0.80 to 1.00.

In addition, the particle size distribution curve in the present invention is measured by a laser diffraction scattering method. The position and height of the peak (A) and D ₅₀ are values specifically measured with a Microtrac (registered trademark) particle size distribution measuring device by the method described in the following Examples.

In FIG. 3, an outline of the mode of ultrasonic treatment in the condition 1 is shown. With the condition 1, in a 50 mL glass beaker 11 having a body inner diameter (L) of 40 mm and a height (H) of 60 mm, 0.06 g of the h-BN powder, detergent ("Marmaremon (registered trademark)", Lion Corporation) A powder sample dispersion (12) in which 0.005g and 50g of water (20℃) are mixed is put, and the tip of the chip 13 of the vibrator of the ultrasonic generator (not shown) is placed on the bottom of the center of the beaker 11 It is set to a height (y) of 1cm from and ultrasonically treated with an output of 150W and an oscillation frequency of 19.5 kHz.

As the ultrasonic generator, specifically, "ultrasonic homogenizer US-150T" (manufactured by Nippon Seiki Seisakusho Co., Ltd.) is used, and as the chip 13 of the vibrator, a contact part with the sample dispersion liquid 12 This stainless steel cylindrical one having a diameter (x) of 18 mm is used.

It can be said that the change in the shape of the particle size distribution curve of the h-BN powder before and after the ultrasonic treatment indicates a change in the agglomerated state of the aggregates of the primary particles of h-BN in the h-BN powder. Among the aggregates, those having a small cohesive strength are disintegrated by the ultrasonic treatment. For this reason, the height of the peak (A) in the particle size distribution curve before and after the ultrasonic treatment and the change in D ₅₀ serve as indicators of the cohesive strength of the aggregate. If the height of the peak (A) does not change before and after the treatment, that is, if a2/a1 is 1, it can be said that the cohesive strength of the aggregate is large.

The h-BN powder has a2/a1 of 0.80 to 1.00, preferably 0.85 to 1.00, and more preferably 0.90 to 1.00. When a2/a1 is 0.8 or more, it can be said that the cohesive strength of the aggregate is sufficient to impart high thermal conductivity and high dielectric strength to the resin or the like.

In addition, the peak A before treatment and the peak A after treatment do not necessarily have the same particle size at the peak position. In some cases, the peak position is shifted toward the side with the smaller particle diameter after the treatment than before the treatment.

The h-BN powder has a d2/d1 of 0.80 to 1.00, preferably 0.85 to 1.00, and more preferably 0.90 to 1.00. When a2/a1 is within the predetermined range and d2/d1 is 1, it can be said that the cohesive strength of the aggregate is very large.

When d2/d1 is 0.8 or more, it can be said that the cohesive strength of the aggregate is sufficient to impart high thermal conductivity and high dielectric strength to the resin or the like.

(BET specific surface area)

The h-BN powder has a BET specific surface area of preferably 0.1 m 2 /g or more and less than 5.0 m 2 /g, more preferably 0.5 to 4.5 m 2 /g, more preferably 1.0 to 4.0 m 2 /g, even more preferably It is preferably 1.5 to 4.0 m 2 /g, more preferably 3.0 to 4.0 m 2 /g.

When the BET specific surface area is 0.1 m 2 /g or more, the familiarity of the h-BN powder with the resin or the like tends to be improved. Further, if it is less than 5.0 m 2 /g, the surface of the h-BN primary particles has smoothness, and the h-BN powder is suitable for imparting high thermal conductivity and high dielectric strength to the resin or the like.

In addition, the BET specific surface area in the present invention is measured by the BET one-point method using a flow method (adsorbate: nitrogen gas). Specifically, it is a value measured by the fully automatic BET specific surface area measuring apparatus described in the following examples.

(Surface of primary particle)

Fig. 4 shows an SEM image of the surface of the primary particles of h-BN constituting the h-BN powder of the present invention. In addition, Fig. 5 shows an SEM image of a cross section of the primary particles of h-BN constituting the h-BN powder of the present invention. As shown in FIGS. 4 and 5, the primary particles are tortoise shell-shaped particles having a small specific surface area and smooth surface. It is considered that the primary particles are in the form of such particles, and are therefore suitable for imparting high thermal conductivity and high dielectric strength to the resin.

(Determinant diameter)

The h-BN powder preferably has a crystallite diameter derived from h-BN (002) plane determined by powder X-ray diffraction measurement of 250 Å or more and less than 375 Å, more preferably 275 Å or more and less than 360 Å, and more preferably 300 Å or more. It is less than 345Å.

When the crystallite diameter is 250 angstroms or more, the h-BN primary particles have an appropriate grain boundary and are preferable in terms of imparting high thermal conductivity to the resin or the like. In addition, if it is less than 375Å, the size of the primary particles of h-BN and the voids between the primary particles are appropriately maintained, thereby suppressing a decrease in the cohesive strength of the aggregates of the primary particles, and the resin It is preferable in terms of imparting high thermal conductivity to the back.

In addition, the crystallite diameter is a value obtained from powder X-ray diffraction measurement using Scherrer's equation, and specifically, it is determined by the method described in the following examples.

[Method for producing hexagonal boron nitride (h-BN) powder]

The method for producing the h-BN powder of the present invention is not particularly limited, but can be suitably produced, for example, by the production method of the present invention as follows.

The production method of the present invention comprises Step 1 of preparing a boron powder, and a mixed powder containing one or two or more boron compounds selected from boron oxoic acid and boron oxide, and the mixed powder in a rare gas atmosphere, 1200 Step 2 of obtaining a temporary calcined powder by temporarily firing at a temperature of not less than 1,800° C., Step 3 of obtaining a granulated powder having a particle diameter of 10 to 200 μm by granulating the temporary calcined powder, and placing the granulated powder in a rare gas atmosphere, It is a manufacturing method including step 4 of melting at 1800°C or more and less than 2000°C to obtain molten powder, and step 5 of calcining the molten powder at 2000 to 2300°C in a nitrogen gas atmosphere to obtain hexagonal boron nitride powder.

The manufacturing method is to sequentially go through the above steps 1 to 5, and after granulating and melting the raw material powder, the surface of the primary particles of h-BN is smoothed by nitriding and firing. The h-BN powder of the present invention having a particle size and having a large cohesive strength of an aggregate of h-BN primary particles can be suitably obtained. The h-BN powder obtained by the above manufacturing method has a tortoise shell shape having a smooth surface of the primary particles (see Fig. 4), has a small BET specific surface area, and imparts high thermal conductivity and high dielectric strength to the resin. It is suitable in that it does.

Hereinafter, the manufacturing method will be described in order of process.

(Process 1: mixing process)

Step 1 is a step of preparing a boron powder and a mixed powder containing one or two or more boron compounds selected from boron oxoic acid and boron oxide. From the viewpoint of producing the h-BN powder of the present invention in high yield, the boron compound in the mixed powder is preferably 50 to 300 parts by mass, more preferably 75 to 200 parts by mass based on 100 parts by mass of the boron powder. , More preferably 90 to 150 parts by mass.

The mixed powder may contain components other than the boron powder and the boron compound as long as it is within the range in which the h-BN powder of the present invention is obtained by the above production method, but the boron powder and the boron compound in the mixed powder The total content is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 100% by mass.

<Boron powder>

As the boron powder, for example, amorphous boron or crystalline boron such as a β rhombohedral crystal can be used. These may be used alone or in combination of two or more.

The boron powder is preferably a fine powder having a D ₅₀ of 0.1 to 5.0 μm from the viewpoint of reactivity. Moreover, D ₅₀ of the said boron powder is calculated|required by the same measurement method as the measurement method of D ₅₀ with respect to the h-BN powder mentioned above.

The boron powder preferably has a boron purity of 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more.

As such finely powdered boron powder, a commercial item can be used.

The mixing method of the boron powder and the boron compound for obtaining the mixed powder is not particularly limited, and can be performed using a mixer generally used to obtain the mixed powder.

<Boron compound>

Examples of the boron compound to be mixed with the boron powder include boron oxo acids such as orthoboric acid (H ₃ BO ₃ ), metaboric acid (HBO ₂ ), and tetraboric acid (H ₂ B ₄ O ₇ ), boron oxide (anhydrous Boric acid: B ₂ O ₃ ). These may be used individually by 1 type, and may use 2 or more types together. Among these, boric anhydride (B ₂ O ₃ ) is preferred from the viewpoints of easiness of mixing with the boron powder, ease of availability, and the like.

The purity of the boron compound is preferably 80% by mass or more, more preferably 85% by mass or more, and still more preferably 90% by mass or more.

(Step 2: Temporary firing step)

Step 2 is a step of temporarily firing the mixed powder at 1200°C or more and less than 1800°C in a rare gas atmosphere to obtain a temporary fired powder.

In the temporary calcination, boron is oxidized by a reaction of boron and the boron compound to produce boron oxide (B ₆ O). It is preferable that the temporary calcination powder contains boron oxyoxide. The generation of boron oxide can be confirmed by powder X-ray diffraction measurement as shown in Fig. 6 (see "Scripta Materialia", vol.99, 2015, p.69-72).

7 shows an SEM image of the temporary firing powder. As shown in Fig. 7, the temporary firing powder has a sharp surface and becomes particles having a star-like shape.

The temporary firing is carried out in a rare gas atmosphere, preferably in an argon gas atmosphere for the reaction to proceed. It is preferable that oxygen gas and nitrogen gas are not contained in the temporary firing atmosphere. The argon gas in the temporary sintering atmosphere is preferably 90% by volume or more in purity, more preferably 95% by volume or more, and still more preferably 98% by volume or more.

From the viewpoint of the temporary calcination temperature and the progress of the boron oxidation reaction, the temperature is 1200°C or more and less than 1800°C, preferably 1350 to 1750°C, and more preferably 1500 to 1700°C. When the temperature is 1200°C or higher, the oxidation reaction of boron easily proceeds, and when it is less than 1800°C, the evaporation rate of the boron compound becomes small and loss of unreacted raw materials can be suppressed.

In addition, from the viewpoint of the homogeneous progress of the reaction, it is preferable to perform the temperature increase at the time of temporary firing in stages, and after raising the temperature to a temperature of less than 1200°C, for example, 800 to 1100°C, the temperature is raised to the temporary firing temperature. desirable.

The temporary firing time for performing the heat treatment at the temporary firing temperature is preferably 1 to 20 hours, more preferably 2 to 15 hours, more preferably 3 to 10 hours from the viewpoint of the progress of the boron oxidation reaction and production cost. It's time.

In addition, when the temporary fired powder is agglomerated, the temporary fired powder may be pulverized and/or classified from the viewpoint of ease of granulation in the granulation process of the subsequent process 3 to be provided to process 3. For example, after pulverizing in a mortar or a common pulverizer, the powder that has passed through a sieve with a particle diameter of 100 µm or less classified through a sieve may be provided to step 3.

The grinding method is not particularly limited, and for example, it can be carried out by a method using a mortar or a known method using a general grinder such as a jaw crusher, a pin mill, and a roll crusher.

In addition, the classification method is not particularly limited, and for example, it can be performed using a sieve having a hole corresponding to the desired particle size, and also means such as a vibrating sieve device, air flow classification, investigation, centrifugation, etc. You can also use

(Process 3: granulation process)

Step 3 is a step of granulating the temporary fired powder to obtain a granulated powder having a particle diameter of 10 to 200 µm.

The particle diameter of the granulated powder is 10 to 200 µm, preferably 20 to 150 µm, more preferably 30 to 100 µm from the viewpoint of obtaining the h-BN powder of the present invention having a predetermined particle size. When the particle diameter is 10 μm or more, it is easy to obtain h-BN powder that imparts high thermal conductivity to the resin, and when it is 200 μm or less, h-BN of a particle size that is easy to maintain molding processability when added to the resin or the like Powder can be obtained suitably.

In addition, the particle diameter here is a value based on the hole of the classifier.

The granulation method is not particularly limited, and a method for obtaining a general granulated powder may be applied. For example, it can be carried out by a dry granulation method such as a method of pressing the temporary fired powder, pulverizing it, and classifying it through a sieve or the like. Alternatively, it may be carried out by a wet granulation method such as a method of spraying and drying the liquid obtained by dispersing the temporary fired powder.

When granulating by the dry granulation method, the pressure molding is a molding method for obtaining a homogeneous granulated powder. For example, after adding a binder to the temporary fired powder and mixing, the mixed powder is added to a mold. It is preferable to put and carry out by uniaxial pressure molding.

Although it does not specifically limit as said binder, For example, resins, such as polyvinyl alcohol (PVA), cellulose, and polyvinylidene fluoride (PVDF), are mentioned. These may be used individually by 1 type, and may use 2 or more types together. Among these, PVA is suitably used.

The amount of the binder added is preferably 0.05 to 2 parts by mass, more preferably 0.1 to 1 part by mass, and still more preferably 0.15 to 0.5 parts by mass, based on 100 parts by mass of the temporary baking powder.

The binder may be added as a solution. For example, when PVA is used, it is added as an aqueous solution having a concentration of preferably 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, and still more preferably 1 to 5% by mass.

In addition, when an aqueous solution of a binder or the like is added, the molded article obtained by pressure molding may be dried and then pulverized if necessary. The drying temperature is preferably 100 to 400°C, more preferably 150 to 400°C, and still more preferably 200 to 300°C. The drying time is preferably 1 to 20 hours, more preferably 2 to 15 hours, and still more preferably 3 to 12 hours.

The pulverization and classification of the molded article can be performed using the same pulverization method and classification method used when obtaining the temporary fired powder as described in step 2 above. For example, it is pulverized with a mortar or a general grinder, and then classified by a sieve or the like to obtain granulated powder within the above particle size range.

When performing the granulation, it is also preferable to add boron oxide (B ₂ O ₃ ) or hexagonal boron nitride (h-BN) to the temporary calcination powder. Any one of these boron compounds to be added may be used, and both may be used in combination.

It is considered that the added boron oxide evaporates when heat-treated in a subsequent step, and increases the surface area by generating voids in the obtained granulated powder, thereby accelerating the nitriding reaction generated by h-BN.

The amount of boron oxide added is preferably 1 to 200 parts by mass, more preferably 10 to 100 parts by mass, based on 100 parts by mass of the temporary calcination powder, from the viewpoints of the promoting effect of the nitriding reaction and the yield of the h-BN powder. , More preferably 30 to 70 parts by mass.

In addition, when h-BN is added, the h-BN becomes the nucleus of the granulated powder, and the yield of the granulated powder is improved, or the nitriding reaction in the nitridation and firing step of the subsequent step 5 An effect such as promoting is obtained. The h-BN to be added is preferably a primary particle or agglomerated particle having a D ₅₀ of 0.1 to 100 µm from the viewpoints of mixingability with the temporary calcination powder, ease of granulation, and the like. Aggregated particles are more preferable as the nuclei of the granulated powder.

The amount of h-BN added is preferably 10 to 300 parts by mass, more preferably 20 parts by mass, based on 100 parts by mass of the temporary calcined powder, from the viewpoint of the promoting effect of the nitriding reaction and the yield of the h-BN powder of the present invention. It is -200 mass parts, More preferably, it is 30-100 mass parts.

(Process 4: melting process)

Step 4 is a step of melting the granulated powder at 1800 to 2300°C in a rare gas atmosphere to obtain a molten powder.

The melting is a heat treatment for melting and smoothing the surface of the granulated powder containing boron oxide (melting point: about 2000°C). The smoothing of the surface of the molten powder can be confirmed by SEM images as shown in the following examples.

8 shows an SEM image of the molten powder. As shown in FIG. 8, the surface of the molten powder melts and becomes smooth particles.

From the viewpoint of obtaining h-BN powder having a BET specific surface area of less than 5 m 2 /g, the molten powder preferably has a BET specific surface area of 2.0 m 2 /g or less, more preferably 1.5 m 2 /g or less, further preferably 1.2 It is less than or equal to m2/g.

The heat treatment is performed in a rare gas atmosphere, preferably in an argon gas atmosphere. It is preferable that oxygen gas and nitrogen gas are not contained in the heat treatment atmosphere. The argon gas in the heat treatment atmosphere preferably has a purity of 90% by volume or more, more preferably 95% by volume or more, and still more preferably 98% by volume or more.

The heat treatment temperature is 1800 to 2300°C, preferably 1850 to 2200°C, and more preferably 1900 to 2100°C, from the viewpoint of melting and smoothing the surface of the granulated powder. If it is 1800°C or higher, the surface of the granulated powder can be melted, and by setting it to 2300°C or lower, fusion of the granulated powders is suppressed.

The heat treatment time is preferably 1 to 10 hours, more preferably 1.5 to 8 hours, and still more preferably 2 to 5 hours from the viewpoint of melting and smoothing of the surface of the granulated powder and production cost.

(Step 5: Nitriding firing step)

Step 5 is a step of firing the molten powder at 2000 to 2300°C in a nitrogen gas atmosphere to obtain h-BN powder. That is, in this step, h-BN powder is obtained as the nitride-fired powder.

The nitridation firing is carried out in a nitrogen gas atmosphere due to the nitridation reaction of the boron oxide of the molten powder. Although rare gas may be contained in the nitriding firing atmosphere, it is preferable that oxygen gas is not contained. The nitrogen gas in the nitriding sintering atmosphere is preferably 90% by volume or more, more preferably 95% by volume or more, and still more preferably 98% by volume or more.

The firing temperature is 2000 to 2300°C, preferably 2050 to 2250°C, and more preferably 2100 to 2200°C from the viewpoints of progress of the nitriding reaction and suppression of decomposition of h-BN. When it is set to 2000°C or higher, the nitridation reaction of the boron oxide easily proceeds, and if it is 2300°C or lower, the decomposition reaction of h-BN is suppressed, which is preferable.

The firing time is preferably 4 to 48 hours, more preferably 6 to 42 hours, and still more preferably 8 to 36 hours from the viewpoints of the progress of the nitriding reaction, suppression of decomposition of h-BN, and production cost. In step 3 (granulation step), when granulating by adding at least one of boron oxide and hexagonal boron nitride to the temporary firing powder, as described above, shorter firing due to the accelerating effect of the nitriding reaction H-BN powder can be obtained in time.

The fired nitriding powder may be pulverized and/or classified to obtain h-BN powder having a predetermined particle size. The pulverization method and classification method are not particularly limited, and can be performed using the same pulverization method and classification method used when obtaining the temporary fired powder described in step 2 above. For example, h-BN powder having a predetermined particle size can be obtained by pulverizing with a mortar or a general grinder and then classifying with a sieve or the like.

The particle diameter of the fired nitride powder is preferably 10 to 200 µm, more preferably 20 to 150 µm, and still more preferably 30 to 100 µm. In addition, the particle diameter here is a value based on the hole of the classifier.

[Composition]

The composition of the present invention includes a substrate including one or two or more selected from resins and rubbers, and the h-BN powder.

The composition is obtained by blending the h-BN powder as a filler for improving thermal conductivity and insulation with respect to the substrate. Since the h-BN powder is easily familiar with the substrate, a homogeneous composition suitable for imparting high thermal conductivity and high dielectric strength to the resin can be formed.

The h-BN powder content in the composition is preferably 10 to 90% by volume, more preferably 20 to 80% by volume, more preferably from the viewpoint of the performance as the filler and the ease of familiarity with the substrate. It is 30 to 70% by volume.

When the content is 10% by volume or more, it is preferable because high thermal conductivity can be imparted to the resin or the like. Further, when the content is 90% by volume or less, voids are less likely to occur in the composition, and a high dielectric strength is imparted to the resin, which is preferable.

In addition, the volume content of the h-BN powder in the composition is the mass content of the h-BN powder measured by the combustion method described in JIS K 7075: 1991 ``Fiber content rate and cavity rate test method of carbon fiber reinforced plastics''. It is calculated by dividing by the density of boron. The total volume of the composition is a value calculated from the specific gravity of boron nitride and the substrate.

(materials)

Resin or rubber is mentioned as a base material of the composition of this invention. Among these, one type may be used alone, or two or more types may be used in combination.

The content of the substrate in the composition is preferably within a range in which high thermal conductivity and high dielectric strength are imparted by the h-BN powder to which the resin or the like is added and mixed, preferably 10 to 90% by volume, more preferably It is preferably 20 to 80% by volume, more preferably 30 to 70% by volume.

The volume content of the substrate in the composition is determined from the total volume calculated from the specific gravity of the boron nitride and the substrate, and the volume content of the h-BN powder.

Examples of the resin include a thermosetting resin, a thermoplastic resin, a thermoplastic elastomer, and an oil.

Examples of the thermosetting resin include epoxy resin, silicone resin, phenol resin, urea resin, unsaturated polyester resin, melamine resin, polyimide resin, polybenzoxazole resin, and urethane resin.

Examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer; Polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and liquid crystal polyester; Polyvinyl chloride resin, acrylic resin, polyphenylene sulfide resin, polyphenylene ether resin, polyamide resin, polyamideimide resin, and polycarbonate resin.

Examples of the thermoplastic elastomer include an olefin-based thermoplastic elastomer, a styrene-based thermoplastic elastomer, a vinyl chloride-based thermoplastic elastomer, a urethane-based thermoplastic elastomer, and an ester-based thermoplastic elastomer.

As said oil, greases, such as silicone oil, are mentioned, for example.

Examples of the rubber include natural rubber, polyisoprene rubber, styrene-butadiene rubber, polybutadiene rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, butadiene-acrylonitrile rubber, isobutylene-isoprene rubber, chloroprene rubber, silicone. Rubber, fluorine rubber, chloro-sulfonated polyethylene, polyurethane rubber, and the like. These rubbers are preferably crosslinked.

The base material is appropriately selected in accordance with properties such as mechanical strength, heat resistance, durability, flexibility, flexibility and the like found in the application of the heat dissipating material obtained by using the composition of the present invention. As the substrate, a thermosetting resin is preferable, and among these, an epoxy resin and a silicone resin are suitably used, and an epoxy resin is more preferable.

<Epoxy resin>

As the epoxy resin used for the substrate, from the viewpoint of the ease of mixing the h-BN powder with the substrate, for example, a liquid epoxy resin at room temperature (25°C), a low softening point that is solid at room temperature (25°C) Epoxy resins are preferred.

As such an epoxy resin, any compound having two or more epoxy groups per molecule may be used. For example, bisphenol A epoxy resin, bisphenol F epoxy resin, glycidyl ether of polycarboxylic acid, epoxidation of cyclohexane derivatives Epoxy resin obtained by, etc. are mentioned. These may be used individually by 1 type, and may use 2 or more types together. Among these, from the viewpoints of heat resistance and ease of handling, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, or an epoxy resin obtained by epoxidation of a cyclohexane derivative is suitable.

It is preferable that the epoxy resin further contains a soluble thermoplastic resin in the epoxy resin from the viewpoint of suppression of segregation of the h-BN powder in the substrate and mechanical properties such as toughness of the heat dissipating material obtained from the composition. .

As such a thermoplastic resin, a thermoplastic resin having a hydrogen bonding functional group is preferable, and examples of the functional group include an alcoholic hydroxyl group, an amide bond, a sulfonyl group, and a carboxyl group. Specific examples of the thermoplastic resin include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, and thermoplastic resins having alcoholic hydroxyl groups such as polyvinyl alcohol and phenoxy resins; Thermoplastic resins having an amide bond such as polyamide, polyimide, polyamideimide, and polyvinylpyrrolidone; Thermoplastic resins having a sulfonyl group such as polysulfone; And thermoplastic resins having a carboxyl group such as polyester, polyamide, and polyamideimide. Among these, a thermoplastic resin having an alcoholic hydroxyl group is preferable, and a phenoxy resin is more preferable.

The blending amount of the thermoplastic resin having a hydrogen bonding functional group is preferably 0.05 to 50 parts by mass, more preferably 1.0 to 30 parts by mass, based on 100 parts by mass of the total of the epoxy resin and the curing agent and curing accelerator used if necessary. It is a mass part, more preferably 5 to 25 mass parts.

In order to cure the epoxy resin, if necessary, a curing agent for an epoxy resin may be used. The curing agent is not particularly limited, and a known curing agent may be appropriately selected and used. Examples of the curing agent include amine-based, phenol-based, acid anhydride-based, imidazole-based, and the like. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the amine curing agent include dicyandiamide, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, m-xylylenediamine, and the like. Aromatic diamines and the like.

Examples of the phenolic curing agent include phenol novolac resin, cresol novolak resin, bisphenol A type novolak resin, and triazine-modified phenol novolak resin.

Examples of the acid anhydride-based curing agent include alicyclic acid anhydrides such as methylhexahydrophthalic anhydride, aromatic acid anhydrides such as phthalic anhydride, aliphatic acid anhydrides such as aliphatic dibasic acid anhydride, and halogenated acids such as chlorendic anhydride. And anhydrides.

Examples of the imidazole-based curing agent include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole , 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, and the like.

The amount of the curing agent used is usually about 0.5 to 1.5 equivalents, and preferably 0.7 to 1.3 equivalents, based on the epoxy resin, from the viewpoint of balance of curability and cured resin properties.

As for the epoxy resin, if necessary, a curing accelerator for an epoxy resin can be used together with the curing agent. The curing accelerator is not particularly limited, and a known one can be appropriately selected and used. Examples of the curing accelerator include 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, 2-ethylimidazole, and 2-isopropylimida Imidazole compounds such as sol, 2-phenylimidazole, and 2-phenyl-4-methylimidazole; 2,4,6-tris(dimethylaminomethyl)phenol; Boron trifluoride amine complex; And triphenylphosphine. These may be used individually by 1 type, and may use 2 or more types together.

The amount of the curing accelerator used is usually about 0.1 to 10 parts by mass, and preferably 0.4 to 5 parts by mass, based on 100 parts by mass of the epoxy resin, from the viewpoint of the balance of curing properties and properties of the cured resin.

<Silicone resin>

As the silicone resin, a mixture of an addition reaction silicone resin and a silicone crosslinking agent may be used.

As said addition reaction type silicone resin, polyorganosiloxane which has an alkenyl group as a functional group is mentioned, for example. Specific examples of the polyorganosiloxane include polydimethylsiloxane having a vinyl group as a functional group, polydimethylsiloxane having a hexenyl group as a functional group, and mixtures thereof.

Examples of the silicone-based crosslinking agent include polyorganosiloxanes having two or more silicon atom-bonded hydrogen atoms in one molecule, and specifically, dimethylsiloxane-methylhydrogensiloxane copolymers with dimethylhydrogensiloxy group end-blocking , Trimethylsiloxy group-terminated dimethylsiloxane-methylhydrogensiloxane copolymer, trimethylsiloxane group-terminated poly(methylhydrogensiloxane), poly(hydrogensilsesquioxane), and the like.

Examples of the curing catalyst for obtaining the silicone resin include platinum-based catalysts such as particulate platinum, particulate platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, and olefin complexes of chloroplatinic acid; Palladium catalyst; And a rhodium catalyst. Among these, a platinum-based catalyst is usually used.

(Other ingredients)

The composition may contain other components other than the base material and the h-BN powder within a range that does not impair the effects of the present invention, but the total content of the base material and the h-BN powder in the composition is 90 mass. It is preferably at least %, more preferably at least 95% by mass, and still more preferably at least 100% by mass.

Examples of the other components include nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride; Insulating metal oxides such as alumina, fibrous alumina, zinc oxide, magnesium oxide, beryllium oxide, and titanium oxide; Insulating carbon components such as diamond and fullerene; Inorganic fillers such as aluminum hydroxide and magnesium hydroxide; Surface treatment agents such as a silane coupling agent to improve the interfacial adhesive strength between inorganic fillers and resins, reducing agents, plasticizers, pressure-sensitive adhesives, reinforcing agents, colorants, heat-resistance improvers, viscosity modifiers, dispersion stabilizers, and solvents.

(Production of the composition)

The method for producing the composition of the present invention is not particularly limited, but for example, when a resin is used as the substrate, it can be produced as follows.

First, as the substrate, a resin, a curing agent and a solvent to be added as necessary are mixed, and the h-BN powder is added and mixed so as to have a desired volume content to obtain a composition.

The mixing method is not particularly limited, and can be performed using a known method or a mixer according to the application purpose of the composition.

[Heating material]

The heat dissipating material of the present invention is made of the above composition. The heat dissipating material is obtained as having excellent thermal conductivity and insulating properties by using the h-BN powder of the present invention described above as a filler.

Examples of the heat dissipating material include various properties such as a sheet, gel, grease, adhesive, and phase change sheet, and the shape thereof is not particularly limited. Among these, for example, the heat dissipation sheet efficiently transfers heat generated from electronic parts such as microprocessors (MPUs), power transistors, and transformers to heat dissipation components such as heat dissipation fins and heat dissipation fans, and the heat dissipation material has excellent thermal conductivity. And because it has insulating properties, it can be suitably applied to such a use.

The heat dissipation sheet is obtained by molding the composition into a sheet shape. When the base material of the composition is a curable resin, it is obtained by molding and curing.

The heat dissipation sheet may be molded by applying the composition on a releasable film such as a resin film with a release layer, for example, by coating the composition with a coating machine, and drying with a far-infrared radiation heater or hot air spraying when the composition contains a solvent. I can. As the release layer, for example, melamine resin or the like is used. Further, as the resin film, for example, a polyester resin such as polyethylene terephthalate is used.

When the base material of the composition is not cured such as a curable resin, the sheet-shaped molded article becomes a heat dissipating sheet.

When the composition is a curable resin, etc., depending on the curing conditions of the curable resin, the molded product in the sheet form is pressed through the releasable film from the side opposite to the coated surface of the releasable film, and heated to cure the molded product. After making it, the said releasable film is peeled, and a heat radiation sheet is obtained.

The heat dissipation sheet has the diffraction peak intensity (I (002)) and the diffraction peak intensity of the (100) plane of the primary particles of h-BN obtained by X-ray diffraction measurement in a direction perpendicular to the thickness direction. It is preferable that the ratio of (I(100)) (I(002)/I(100)) is 7.0 to 15.0.

In the crystal of h-BN, the thickness direction is a (002) plane, that is, the c-axis direction, and the in-plane direction is a (100) plane, that is, the a-axis direction. When the primary particles of h-BN are unoriented, the I(002)/I(100) is about 6.7 ("JCPDS powder X-ray diffraction database" No.34-0421[BN] crystal density value [Dx]) ]). In high crystal h-BN, the I(002)/I(100) is generally greater than 20.

As the I(002)/I(100) increases, the surface direction (a-axis direction) of the h-BN primary particles is oriented in the in-plane direction of the heat dissipation sheet, and the thermal conductivity in the thickness direction of the heat dissipation sheet decreases. easy. Conversely, as the I(002)/I(100) is smaller, the primary particles of h-BN are randomly oriented in the heat dissipation sheet, and the thermal conductivity of the heat dissipation sheet in the thickness direction tends to increase. As described above, I(002)/I(100) indicates the orientation of the primary particles of h-BN, and may be one index of thermal conductivity.

The I(002)/I(100) is actually 7.0 or more, and is preferably 15.0 or less, more preferably 12.0 or less, and still more preferably 9.5 or less from the viewpoint of obtaining high thermal conductivity of the heat dissipating sheet.

Further, the heat dissipation sheet may be laminated or buried in at least one surface and inside the sheet with other auxiliary members such as a sheet, fibrous, and mesh for the purpose of improving or reinforcing workability. Further, the heat dissipation sheet may have an adhesive layer formed on at least one side of the heat dissipation sheet from the viewpoint of convenience in use.

(Example)

Hereinafter, the present invention will be described in detail by examples, but the present invention is not limited to the following examples.

[Various analysis and evaluation in the production of h-BN powder]

Various analysis and evaluation methods for the h-BN powder in each of the following production examples and the powder sample in the production process are shown below.

(Content of impurities in h-BN powder)

Using a nitrogen-oxygen analyzer ("TC-600", manufactured by LECO Japan Co., Ltd.), the oxygen content and nitrogen content in the h-BN powder sample were measured. From the nitrogen content, as described above, the total impurity content in the h-BN powder sample was calculated, and the value obtained by subtracting the oxygen content was taken as the content of boron as an impurity element.

(D ₅₀ of boron powder and h-BN powder)

A powder sample dispersion was prepared in which 0.06 g of each powder sample, 0.005 g of detergent ("Marmaremon (registered trademark)", manufactured by Lion Corporation), and 50 g of water (20°C) were mixed. While the dispersion was stirred at 400 rpm with a magnetic stirrer, the particle size distribution was measured with a Microtrac (registered trademark) particle size distribution measuring device ("MT3300EXII", manufactured by Nikiso Corporation), and D ₅₀ was determined.

(a2/a1 and d2/d1 of h-BN powder)

for the h-BN powder sample, wherein the D _50, as in the case obtained by measuring the particle size distribution for a sample dispersion of h-BN powder, and to obtain a particle size distribution curve. In the particle size distribution curve, the height a1 of the peak (A) in the range of 10.0 µm or more and less than 100.0 µm and D ₅₀ (d1) were obtained.

In addition, the sample dispersion of h-BN powder prepared in the same manner as the above sample dispersion was placed in a 50 mL glass beaker having a body inner diameter (L) of 40 mm and a height (H) of 60 mm, and an ultrasonic generator (``Ultrasonic homogenizer US-150T ", Nippon Seiki Seisakusho Co., Ltd. product, output 150W, oscillation frequency 19.5kHz) ultrasonication was carried out for 1 minute. In the ultrasonic treatment, as shown in Fig. 3, the tip of the chip of the vibrator of the ultrasonic generator (made of stainless steel, cylindrical shape with a diameter (x) of 18 mm) 13 is 1 cm high from the bottom of the central portion of the beaker. It was set to (y) and performed.

About the sample dispersion liquid after ultrasonic treatment, it carried out similarly to the above, and the particle size distribution was measured, and the particle size distribution curve was obtained. In the particle size distribution curve, the height a2 and D ₅₀ (d2) of the peak (A) were calculated, and a2/a1 and d2/d1 were calculated.

As a representative example of the particle size distribution curve for the h-BN powder obtained in the following Preparation Example, the particle size distribution curve for the h-BN powder of Preparation Example 1 is shown in Fig. 1, and the particle size distribution for the h-BN powder of Preparation Example 3 The curve is shown in FIG. 2. The left side of each figure is before ultrasonic treatment, and the right side is after ultrasonic treatment.

(BET specific surface area of h-BN powder and molten powder)

About the powder sample, the specific surface area was measured by the BET 1-point method by the flow method (adsorbent quality: nitrogen gas) with a fully automatic BET specific surface area measuring device ("Multisorb 16", manufactured by Yuasa Ionics Co., Ltd.).

(crystallite diameter of h-BN powder)

For the h-BN powder sample, powder X-ray diffraction measurement was performed with an X-ray diffraction measuring device ("X'Pert PRO", manufactured by Panartical Corporation, target: copper, Cu-Kα1 ray), and the following formula (3) The crystallite diameter D[Å] was calculated from the Scherrer equation shown.

D=(K·λ)/(β·cosθ) (3)

In Formula (3), K: Scherrer constant, λ: X-ray (Cu-Kα1 ray) wavelength [Å], β: broadening of the diffraction line (half peak width) [radian], θ: Bragg angle [radian].

In the calculation, K = 0.9 and λ = 1.54059 [Å]. In addition, β used the value calculated|required by the correction formula represented by following formula (4).

β=(β ₀ ² -β _i ² ) ^0.5 (4)

In formula (4), β ₀ : peak half-value width derived from the h-BN (002) plane, β _i : half-value width derived from the apparatus by the standard sample (Si).

(X-ray diffraction measurement of temporary firing powder)

With respect to the temporary calcination powder sample, powder X-ray diffraction measurement was performed with an X-ray diffraction measuring device used to measure the crystallite diameter of the h-BN powder, and it was confirmed that boron nitrous oxide was generated.

[Preparation of h-BN powder]

(Production Example 1 (Example 1))

<Step 1: mixing process>

100 parts by mass of amorphous boron (manufactured by HCStarck, Grade I, D ₅₀ : 0.6 µm, purity 95% by mass or more) 100 parts by mass of boron oxide (manufactured by Kanto Chemical Co., Ltd., Cica 1st grade, purity exceeding 90% by mass) It was added and mixed with a mixer to prepare a mixed powder.

<Step 2: Temporary firing step>

The mixed powder obtained in the above step 1 was placed in a crucible made of graphite, and the temperature in the furnace was raised from room temperature to 1000°C for 15 minutes in an atmosphere of argon gas (purity 99.99 vol%, flow rate 2 L/min), The temperature was raised from 1000° C. to 1600° C. in 45 minutes, maintained at 1600° C. for 6 hours, and temporarily fired to obtain a temporary fired powder.

After the temporary fired powder was pulverized with a mortar, it was treated for 5 minutes by using a sieve having a hole of 75 μm with a low tap sieve shaker to obtain a powder passed through the sieve.

The temporary fired powder obtained by classification was subjected to X-ray diffraction measurement. 6 shows the X-ray diffraction spectrum. As shown in Fig. 6, it was confirmed that boron nitrous oxide was generated.

7 shows an SEM image of the temporary fired powder obtained by classification. As shown in Fig. 7, it was observed that the temporary fired powder had a sharp surface and had a star-like shape.

<Step 3: Granulation step>

Mixer by adding 10 parts by mass of a 2.5% by mass aqueous solution of PVA ("POVAL (registered trademark) PVA-205", manufactured by Kuraray) as a binder to 100 parts by mass of the temporary fired powder (powder passed through a sieve) obtained in step 2 above. Mixed with.

The temporary fired powder mixed with the binder was uniaxially press-molded at 60 MPa in a hand press device, and then dried at 200°C for about 3 hours.

After the dried molded product was pulverized with a mortar, a sieve having 75 µm and 32 µm holes was overlapped with a sieving shaker and treated for 5 minutes to classify, and a powder that did not pass through a sieve having a hole 32 µm was obtained as granulated powder.

<Process 4: melting process>

The granulated powder obtained in step 3 was heated in an atmosphere furnace under an atmosphere of argon gas (purity 99.99 vol%, flow rate 2 L/min), the temperature in the furnace was raised from room temperature to 1980°C for 120 minutes, and then at 1980°C for 3 hours. It was held and melted to obtain a molten powder.

8 shows an SEM image of the molten powder. As shown in Fig. 8, it was confirmed that the molten powder was a particle whose surface was melted and smoothed.

The BET specific surface area of the molten powder was 0.5 m 2 /g.

<Step 5: Nitriding firing step>

The atmospheric gas in the atmosphere in which the step 4 was performed is switched to nitrogen gas (purity 99.995 vol%, flow rate 2 L/min) to raise the temperature in the furnace to 2100° C., and maintained for 36 hours to nitrate and fire the molten powder. Got it.

After pulverizing the fired nitriding powder with a mortar, it was classified by processing for 5 minutes using a sieve having a hole of 75 μm with a low tap sieve shaker, and the powder passed through the sieve was obtained as the h-BN powder of Example 1.

The h-BN powder obtained by classification was subjected to X-ray diffraction measurement. 9 shows the X-ray diffraction spectrum.

(Production Example 2 (Comparative Example 1))

In step 5 (nitridation firing step) of Production Example 1, the temperature in the furnace was set to 1980° C., and the heat treatment time was set to 3 hours, except that the h-BN powder of Comparative Example 1 was obtained in the same manner as in Production Example 1. .

(Production Example 3 (Comparative Example 2))

h-BN powder raw material (D ₅₀ : 0.67 μm, BET specific surface area 10 m 2 /g, crystallite diameter 260 Å) 65 parts by mass of boron oxide (Kanto Chemical Co., Ltd., Cica 1st grade, purity exceeding 9% by mass) 35 The mass part was added and mixed with a mixer. To this, 13 parts by mass of boron carbide (manufactured by Riken Corundum Co., Ltd., D ₅₀ : 3 µm), and 10 parts by mass of PVA ("POVAL (registered trademark) PVA-205", manufactured by Kuraray) 2.5 parts by mass of aqueous solution were added thereto. It mixed with a mixer, and a mixed powder was obtained.

The mixed powder was uniaxially press-molded at 60 MPa in a hand press, and then dried at 200°C for about 3 hours.

The dried molded product was fired at 2000°C for 12 hours in a nitrogen gas (purity 99.995 volume%, flow rate 2 L/min) atmosphere in an atmosphere furnace to obtain a fired product.

After the obtained fired product was pulverized with a mortar, it was classified by processing for 5 minutes using a sieve having a hole of 75 μm with a low tap sieve shaker, and the powder passed through the sieve was obtained as h-BN powder of Comparative Example 2.

(Production Example 4 (Comparative Example 3))

The commercially available h-BN sintered body (density 1.92 g/cm 3, purity 99.5 mass% or more) was pulverized with a mortar, and then treated for 5 minutes using a sieve with a hole of 75 μm with a low tap sieve shaker, and classified. The powder was obtained as the h-BN powder of Comparative Example 3.

(Production Example 5 (Example 2))

In step 3 (granulation step) of Production Example 1, PVA ("POVAL (registered trademark) PVA-205", manufactured by Kuraray) as a binder based on 100 parts by mass of the temporary fired powder (powder passed through a sieve) 10 parts by mass of a 2.5% by mass aqueous solution and 38 parts by mass of the h-BN powder obtained in Production Example 4 were added and mixed with a mixer, except for that, in the same manner as in Production Example 1, the h-BN powder of Example 2 was obtained.

Moreover, the BET specific surface area of the molten powder was 1.0 m 2 /g.

[Manufacture of heat-dissipating sheet]

(Examples 3 and 4 and Comparative Examples 4 to 6)

Using each h-BN powder obtained in the above production example, a composition was prepared as follows, and a heat dissipating sheet was produced using the composition.

At room temperature (25°C), 90 parts by mass of a liquid bisphenol A epoxy resin ("YD-128", manufactured by Shinnittetsu Sumikin Chemical Co., Ltd., epoxy equivalent 184 to 194 g/eq), and a phenoxy resin ("YP -50S", Shinnittetsu Sumikin Chemical Co., Ltd. product, purity 99.0 mass% or more) 10 mass parts of mixtures were used as a base material. The h-BN powder was added and mixed to the substrate so that the content of the h-BN powder in the composition was 65% by volume. In addition, 153 parts by mass of methoxypropanol ("Hisolve MP", manufactured by Toho Chemical Industry Co., Ltd.) (170 parts by mass per 100 parts by mass of bisphenol A epoxy resin) was added as a viscosity modifier, and a stirring/degassing device ( A composition was prepared by stirring and mixing in "Mazel Star (registered trademark)", manufactured by Kurashiki Bowseki Co., Ltd.). In addition, the volume content of the h-BN powder was determined from the specific gravity of the h-BN powder 2.27 g/cm 3 and the specific gravity of the bisphenol A epoxy resin 1.17 g/cm 3.

The composition was coated on a releasable film made of polyethylene terephthalate with a film thickness of 350 μm with a coater, and dried in air at 50° C. for 10 minutes and under vacuum for 10 minutes to obtain a sheet formed body.

The two sheet molded bodies were stacked so that the molded bodies were in contact with each other, and then roll-pressed to make each thickness of the sheet molded body 200 µm. Thereafter, the laminated sheet molded body was heat-pressed at 120° C. for 30 minutes to cure, and a heat-radiating sheet having a length of 10 cm, a width of 10 cm and a thickness of 300 μm was produced.

[Evaluation of heat dissipation sheet]

The following various evaluations were performed on each heat dissipation sheet manufactured in the above example.

(I(002)/I(100) of the primary particles of h-BN)

With respect to the heat dissipation sheet, an X-ray diffraction measurement device ("X'Pert PRO", manufactured by Panasonic Corporation, target: copper, Cu-Kα1 line) is used for 1 of h-BN in a direction perpendicular to the thickness direction of the heat dissipation sheet. The ratio (I(002)/I(100)) of the diffraction peak intensity (I(002)) on the (002) plane of the secondary particles and the diffraction peak intensity (I(100)) on the (100) plane was measured.

(Thermal conductivity)

The thermal diffusivity [m 2 /s] of the heat dissipation sheet was measured with a xenon flash analyzer ("LFA447 NanoFlash", manufactured by NETZSCH). The value obtained by multiplying the measured value by the specific heat and density of the heat dissipating sheet was taken as the thermal conductivity [W/(m·K)] in the thickness direction of the heat dissipating sheet. In addition, the specific heat is boron nitride 0.8 J/(g·K), the resin component (from base material) is 1.8 J/(g·K) theoretical value (room temperature (25°C)), and the density is boron nitride 2.27 The g/cm 3 and the resin component (derived from the substrate) were calculated using the theoretical value (room temperature (25°C)) of 1.17 g/cm 3.

When the thermal conductivity was 13 W/(m·K), it was determined as having excellent thermal conductivity.

(Insulation)

The insulation breakdown voltage (insulation breakdown voltage) [kV/mm] of the heat dissipation sheet was measured with a breakdown voltage/insulation resistance measuring device ("TOS9201/5101", manufactured by Kikusui Denshi Kogyo Co., Ltd.) at a boosting speed of 0.1 kV/sec. .

In addition, the measured value of the insulation breakdown voltage of Example 3 in Table 1 below was set to 1 (reference), and the other Examples and Comparative Examples were expressed as relative ratios. When the relative ratio was 0.8 or more, it was judged as having excellent insulation.

About the h-BN powder in the said Example and the comparative example, and the heat-radiating sheet manufactured using this, various evaluation results are put together in Table 1, and are shown.

As can be seen from Table 1, the particles produced by boron nitrous oxide have a predetermined particle size and have a predetermined particle size by smoothing the surface through a granulation process and a melting process, followed by nitriding firing. It was confirmed that h-BN powder having high cohesive strength of the aggregate was obtained, and a heat dissipating sheet excellent in thermal conductivity and insulation was obtained by using this.

11: 50mL glass beaker
12: sample dispersion
13: Chip of the vibrator of the ultrasonic generator

Claims (10)

As a hexagonal boron nitride powder comprising an aggregate of primary particles of hexagonal boron nitride,
As an impurity element, the content of boron atoms not constituting hexagonal boron nitride is 5.00 to 30.00 mass%, and the oxygen content is 0 to 1.00 mass%,
In the particle size distribution curve showing the frequency distribution on a volume basis, the peak is in the range of 10.0 μm or more and less than 100.0 μm, and the 50% volume cumulative particle size D ₅₀ (d1) is 30.0 to 200.0 μm,
The ratio (a2/a1) of the peak height (a1) before treatment and the peak height (a2) after treatment when the hexagonal boron nitride powder is subjected to ultrasonic treatment for 1 minute under the following condition 1 is 0.80 to 1.00, , Further, the 50% volume cumulative particle diameter D ₅₀ (d1) and 50% volume cumulative particle diameter D ₅₀ (d2) ratio (d2 / d1) of hexagonal boron nitride powder is from 0.80 to 1.00 in the treated before the treatment.
[Condition 1] In a 50 mL glass beaker having a body inner diameter of 40 mm and a height of 60 mm, 0.06 g of the hexagonal boron nitride powder, detergent ("Marmaremon (registered trademark)", manufactured by Lion Corporation) 0.005 g and water (20) ℃) 50g of the mixed powder sample dispersion is put, and the tip of the ultrasonic generator's vibrator is set at a height of 1cm from the bottom of the center of the beaker, and ultrasonically treated with an output of 150W and an oscillation frequency of 19.5 kHz. The method of claim 1,
A BET specific surface area of 0.1 m 2 /g or more and less than 5.0 m 2 /g, and the surface of the primary particles is a turtle shell-shaped hexagonal boron nitride powder. The method according to claim 1 or 2,
Hexagonal boron nitride powder having a crystallite diameter derived from (002) plane of hexagonal boron nitride determined by powder X-ray diffraction measurement of 250 Å or more and less than 375 Å. As a method for producing the hexagonal boron nitride powder according to claim 1 or 2,
Step 1 of preparing a boron powder and a mixed powder containing one or two or more boron compounds selected from boron oxoic acid and boron oxide, and
Step 2 of temporarily firing the mixed powder at 1200°C or more and less than 1800°C in a rare gas atmosphere to obtain a temporary fired powder, and
Step 3 of granulating the temporary fired powder to obtain a granulated powder having a particle diameter of 10 to 200 μm, and
Step 4 of melting the granulated powder at 1800 to 2300° C. in a rare gas atmosphere to obtain a molten powder, and
A method for producing hexagonal boron nitride powder, comprising Step 5 of calcining the molten powder at 2000 to 2300°C in a nitrogen gas atmosphere to obtain hexagonal boron nitride powder. The method of claim 4,
A method for producing a hexagonal boron nitride powder in which the temporary calcination powder obtained in step 2 contains boron oxynitride. The method of claim 4,
In the step 3, a method for producing a hexagonal boron nitride powder is granulated by adding at least one of boron oxide and hexagonal boron nitride to the temporary calcined powder. A composition comprising a base material consisting of one or two or more selected from resins and rubbers, and the hexagonal boron nitride powder according to claim 1 or 2. A heat dissipating material comprising the composition according to claim 7. The method of claim 8,
Heat-dissipating material that is a heat-dissipating sheet. The method of claim 9,
The diffraction peak intensity (I(002)) on the (002) plane and the diffraction peak on the (100) plane of the primary particles of hexagonal boron nitride obtained by X-ray diffraction measurement in a direction perpendicular to the thickness direction of the heat dissipation sheet A heat dissipating material having a strength (I(100)) ratio (I(002)/I(100)) of 7.0-15.

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